1. Field of the Invention
The present invention relates to a grommet, which is fitted into a through hole of a panel of a vehicle or the like, and a wire harness is inserted therethrough.
2. Description of Related Art
FIG. 1 shows such a grommet. A grommet 1 has a thin small diameter drum portion 2, a thin tapered portion 3 and a thick large diameter drum portion 4 through which a wire harness 7 is inserted. The grommet 1 is formed by an elastic material such as rubber as a unit. A fitting groove 4b which is fitted into a through hole 9a of a panel 9 for vehicle is formed on an outer wall surface 4a of the large diameter drum portion 4.
An inner drum portion 5 which is connected with the small diameter drum portion 2 is formed to the inside of the tapered portion 3 so as to protrude from the tapered portion 3. A lip portion 6 is formed on the outer wall surface 4a of the large diameter drum portion 4 so as to closely contact with the panel 9 and protrude from the outer wall surface 4a to the outside. The art of the grommet 1 is disclosed in Japanese Patent Application Laid-Open No. 10-92243 (1998).
The conventional grommet 1 is formed by using a molding die 8 shown in FIG. 2. The molding die 8 is composed of an upper die 8A, a middle plate 8B, a lower die 8C and a core 8D. After the grommet 1 is molded by using the molding die 8, it is necessary to firstly pull out the upper die 8A and the middle plate 8B in a direction of an arrow A in FIG. 2 in order to take out the grommet from the molding die 8. However, in order to ensure the release the lip portion 6 with large undercut amount from the middle plate 8B, the middle plate 8B should be moved in the direction of the arrow A in FIG. 2, but a thick portion 4C of the large diameter drum portion 4 disturbs the mold release. Therefore, in order to release the middle plate 8B from the large diameter drum portion 4, the middle plate 8B is forcibly pulled out of the large diameter drum portion 4.
However, even if the grommet 1 is formed by rubber or the like, since the large diameter drum portion 4 has the thick portion 4C, and the forcible release utilizing the elastic material is restricted. This influences the molding cycle, and causes a deterioration in productivity.
The present invention has been accomplished to solve the above problem and it is an object of the present invention to provide a grommet, which is capable of improving productivity.
The first aspect of the present invention provides a grommet including a small diameter drum portion through which a wire harness is inserted, and a large diameter drum portion provided adjacently to the small diameter drum portion and through which the wire harness is inserted, and a fitting groove provided on an outer wall surface of the large diameter drum portion and fitted into a through hole of a panel, the improvement comprising: a lip portion which is provided on an outer side from the outer wall surface of the large diameter drum portion and contacts with the panel; and a thin-wall portion formed on a rear surface side of the large diameter drum portion.
According to the first aspect of the present invention, a rear surface side of the large diameter drum portion is thinned. Therefore, when the grommet is molded by a molding die, the grommet elastically deforms to the rear surface side of the large diameter drum portion easily, and released is assured. The lip portion with a large undercut amount is formed thin on the large diameter drum portion. As a result, the release characteristics at the time of molding the grommet are improved greatly, and the productivity of the grommet is improved.
The second aspect of the present invention provides a grommet according to the first aspect of the present invention, further comprising; a soundproof film for forming an air layer on the inside of the large diameter drum portion, wherein the thin-wall portion is provided between the lip portion and the soundproof film.
According to the second aspect of the present invention, the thin-wall portion is provided between the lip portion and the soundproof film. Therefore, the easy elastic deformation of the lip portion to the thin-wall portion for release is assured.
The third aspect of the present invention provides a grommet according to the second aspect of the present invention, wherein the soundproof film extends from an inner end of the thin-wall portion to a position where it contacts with the wire harness.
According to the third aspect of the present invention, the soundproof film extends from the inner end of the thin-wall portion of the large diameter drum portion to a position where it comes closely into contact with the wire harness. The soundproof film forms an air layer in the large diameter drum portion. Therefore, when the lip portion elastically deforms at the time of release, the lip portion does not interfere with the soundproof film. Therefore, the grommet with excellent soundproof characteristics is released from the molding die easily and securely.
The fourth aspect of the present invention provides a grommet according to the third aspect of the present invention, wherein the lip portion is formed into an approximate V-shape, and the thin-wall portion is provided between an outer wall of the lip portion and the soundproof film.
The fifth aspect of the present invention provides a grommet according to the first aspect of the present invention, wherein the small diameter drum portion is formed thin and the large diameter drum portion is formed thick.
The sixth aspect of the present invention provides a grommet according to the first aspect of the present invention, wherein the grommet is formed by an elastic material so that the small diameter drum portion, the large diameter drum portion, the fitting groove and the lip portion are integral.